One especially promising area of immunotherapy has been adoptive transfer of genetically programmed, patient-derived blood lymphocytes transfected with chimeric antigen receptor genes (CARs) to combine the effector functions of T lymphocytes with the ability of antibodies to recognize pre-defined surface antigens with high specificity in a non-MHC restricted manner. The success of CAR-T cell therapy depends on targeting an antigen that is highly expressed in tumors, but at minimal levels in normal tissues. To date, only cancer cells have been targeted, however, it is well established that beyond a minimal size, cancer progression is dependent on a stroma that contains blood vessels, inflammatory cells, and fibroblasts. The underlying hypothesis of this proposal is that destruction of stromal cells using CAR-T cells will alter the tumor microenvironment leading to inhibition of tumor growth in lung cancer. Because stromal cells are diploid and genetically stable, this could reduce the incidence of immune evasion. To test this hypothesis, we will target fibroblast activation protein (FAP), a stromal cell-surface protein highly expressed on cancer-associated fibroblasts in most human epithelial cancers, including lung cancers, but present at very low levels on normal adult tissues, except healing wounds and in some chronic inflammatory conditions. We propose the following specific aims: Aim 1. Evaluate the efficacy of retrovirally-transduced murine FAP-CAR T cells to inhibit the growth of lung cancers (using three mouse lung cancer models). Aim 2. Evaluate the mechanisms by which retrovirally-transduced murine FAP-CAR T cells inhibit the growth of tumors. Aim 3. Evaluate the combination of FAP-CAR T cells with chemotherapy (Aim 3A) and with a tumor-cell targeted CAR (mesothelin-CAR) (Aim 3B). Aim 4. Evaluate the efficacy and mechanisms of lentivirally-transduced human FAP-CAR T cells to inhibit the growth of human lung cancers in immunodeficient mice. In addition to obtaining answers to the scientific questions described above, completion of these aims will provide the preclinical data needed to implement a clinical trial for lung cancer. Funding for a potential FAP-CAR clinical trial is not requested in this proposal, but will be obtained through other support. If our strategy proves effective, this project will likely have additional significace beyond lung cancer, since FAP could be targeted in many tumors.